The reason I ask is that during a game a player should cover 3 miles, and a midfielder/winger might cover double that.
What you have to remember that during a game, there is a big mix of running. There will be a some jogging, lots of sustained 70-80% and a bits of 100% flat out. So this must be accounted for in training.
Just doing a load of running at a slow set pace wont do you a huge amount of good. It might increase your cardio a bit, but generally, its not going to make a huge difference to your game.
Going to the training session will be a good idea, as you will be able to participate in small games and drills that are perfect for tailoring your fitness level to hockey. It also means you can break up pure fitness stuff with skills and drills.
However, as this is not possible at the moment, you will need to mix up your sessions. As a starting point for a session, you should go for a light jog, the kind of pace where you can comfortably talk to someone whilst running. Perhaps do this for 7-10 minutes initially. Then some stretching, gentle at first, holding the stretch for a few seconds (try and avoiding bouncing in the stretch).
After this preparation you should be feeling pretty good, nice and warm, and ready to go. Perhaps do another few minutes of slightly higher intensity jogging just to make sure your blood is pumping nicely.
One of the old school favorites is what is called a Doggy:
Baseline - 25 - Baseline - 50 - Baseline - 75 - baseline - 100 - baseline
You should try and compete this at a steady pace. The idea is to maintain you speed throughout the whole distance. The stopping and turning is something you will do a lot of in a game too.
I would say do a doggy at the start of your session, and another at the end of the end. Try and get as close to the time set in the first when running the second.
Will add some more later, as I am at work at the moment!!